A157007 Numbers k such that 2^k + 27 is prime.

1, 2, 4, 5, 8, 10, 13, 14, 16, 40, 41, 44, 86, 110, 125, 133, 134, 145, 154, 184, 194, 301, 308, 320, 685, 1001, 1066, 1496, 1633, 2005, 2864, 3241, 6286, 11585, 12854, 16514, 16540, 19246, 24538, 28705, 57644, 65366, 85276, 89113, 194854, 266680, 376790, 478088

Offset

1,2

Comments

a(49) > 5*10^5. - Robert Price, Nov 06 2015

Links

Table of n, a(n) for n=1..48.

Henri Lifchitz and Renaud Lifchitz, Search for 2^n+27, PRP Top Records.

Example

For k = 1, 2^1 + 27 = 29.
For k = 2, 2^2 + 27 = 31.
For k = 4, 2^4 + 27 = 43.

Mathematica

Delete[Union[Table[If[PrimeQ[2^n + 27], n, 0], {n, 1, 2000}]], 1]
Select[Range[5000], PrimeQ[2^#+27]&] (* Harvey P. Dale, Mar 24 2011 *)

Prog

(PARI) for(n=1, 1e3, if(isprime(2^n+3^3), print1(n", "))) \\ Altug Alkan, Oct 04 2015
(Magma) [n: n in [0..1000] | IsPrime(2^n+27)]; // Vincenzo Librandi, Oct 05 2015

Crossrefs

Cf. A057733, A094076, A104071, A123250.

Cf. A019434 (primes 2^k+1), A057732 (2^k+3), A059242 (2^k+5), A057195 (2^k+7), A057196 (2^k+9), A102633 (2^k+11), A102634 (2^k+13), A057197 (2^k+15), A057200 (2^k+17), A057221 (2^k+19), A057201 (2^k+21), A057203 (2^k+23), A157006 (2^k+25), this sequence (2^k+27), A156982 (2^k+29), A247952 (2^k+31), A247953 (2^k+33), A220077 (2^k+35).

Sequence in context: A342541 A365315 A179509 * A173509 A007729 A174868

Adjacent sequences: A157004 A157005 A157006 * A157008 A157009 A157010

Keyword

nonn

Author

Edwin Dyke (ed.dyke(AT)btinternet.com), Feb 20 2009

Extensions

More terms from Harvey P. Dale, Mar 24 2011

a(33)-a(42) from Robert Price, Oct 04 2015

a(43)-a(47) discovered by Henri Lifchitz and Lelio R Paula from Lifchitz link by Robert Price, Oct 04 2015

a(48) from Robert Price, Nov 06 2015

Status

approved